Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 260850
SPC AC 260849

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0349 AM CDT Mon Jun 26 2017

Valid 291200Z - 041200Z

On Thu/D4, cyclonic, but almost zonal flow aloft will persist from
the central Rockies eastward into the northeastern states, with
various low-amplitude shortwave features within the flow. The
primary trough of interest will affect the central Plains during the
day, with midlevel flow on the order of 30-40 kt overspreading a
quasi-stationary boundary extending roughly along the latitude of
I-80. Along and south of this front, an increasingly moist air mass
will reside with dewpoints largely in the upper 60s F.

By Thu afternoon, a weak surface low is expected to form around the
OK panhandle, with strong heating resulting in steep lapse rates
from KS southward across west TX, and pockets of heating eastward
along I-70 into MO. Main foci for development will be the surface
low/dryline in central KS, warm advection near the main front across
NE, and any outflow boundaries that may exist from eastern KS into
IL from remnant early-day storms. Long hodographs for this latitude
and time of year, combined with veering low-level winds with height,
especially across KS, will likely lead to a few supercells, with
more widespread storms from NE across the mid to lower MO Valley.

Elsewhere on D4, rapid low-level warm advection will occur across
the Northeast as an upper trough lifts across the Canadian
Maritimes, and a low-amplitude shortwave trough continues eastward
across the Great Lakes. Weak instability will spread into western PA
and NY, along with increased mean wind speeds which may support a
marginal severe wind threat.

For D5/Fri and beyond, predictability becomes quite low given the
likelihood of one or more MCS`s across the central Plains into the
Midwest. However, at least some low-end severe risk is likely at
some point as the shortwave trough over the Plains shifts slowly
eastward during the D5-D8 period.

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